import { A_START_CHAR, B_START_CHAR, C_START_CHAR, A_CHARS, B_CHARS, C_CHARS } from './constants'

// Match Set functions
const matchSetALength = (string) => string.match(new RegExp(`^${A_CHARS}*`))[0].length
const matchSetBLength = (string) => string.match(new RegExp(`^${B_CHARS}*`))[0].length
const matchSetC = (string) => string.match(new RegExp(`^${C_CHARS}*`))[0]

// CODE128A or CODE128B
function autoSelectFromAB(string, isA) {
  const ranges = isA ? A_CHARS : B_CHARS
  const untilC = string.match(new RegExp(`^(${ranges}+?)(([0-9]{2}){2,})([^0-9]|$)`))

  if (untilC) {
    return untilC[1] + String.fromCharCode(204) + autoSelectFromC(string.substring(untilC[1].length))
  }

  const chars = string.match(new RegExp(`^${ranges}+`))[0]

  if (chars.length === string.length) {
    return string
  }

  return chars + String.fromCharCode(isA ? 205 : 206) + autoSelectFromAB(string.substring(chars.length), !isA)
}

// CODE128C
function autoSelectFromC(string) {
  const cMatch = matchSetC(string)
  const length = cMatch.length

  if (length === string.length) {
    return string
  }

  string = string.substring(length)

  // Select A/B depending on the longest match
  const isA = matchSetALength(string) >= matchSetBLength(string)
  return cMatch + String.fromCharCode(isA ? 206 : 205) + autoSelectFromAB(string, isA)
}

// Detect Code Set (A, B or C) and format the string
export default (string) => {
  let newString
  const cLength = matchSetC(string).length

  // Select 128C if the string start with enough digits
  if (cLength >= 2) {
    newString = C_START_CHAR + autoSelectFromC(string)
  } else {
    // Select A/B depending on the longest match
    const isA = matchSetALength(string) > matchSetBLength(string)
    newString = (isA ? A_START_CHAR : B_START_CHAR) + autoSelectFromAB(string, isA)
  }

  return newString.replace(
    /[\xCD\xCE]([^])[\xCD\xCE]/, // Any sequence between 205 and 206 characters
    (match, char) => String.fromCharCode(203) + char
  )
}
